Most modem laser printers and an increasing number of faxes, copiers and other image-transfer devices utilize self-contained, replaceable toner cartridges. These cartridges include a tank or tanks filled, typically, with a one-part toner, a toner metering system that includes a developer roller and a photosensitive drum. Such cartridges are disposable, but are sufficiently complex so that they are normally recycled after the toner supply in the tank or tanks is exhausted.
A continuing annoyance that plagues both new and remanufactured toner cartridges is the leakage of toner during shipment. Various techniques have been employed to limit toner leakage. Most of these techniques involve the placement of a removable seal adjacent the outlet of the toner tank. During shipment, toner particles, which are sized a few microns or less, act almost as a fluid, tending to slosh about the tank and exhibit hydraulic pressure-like effects. During rough shipment, the pressure often defeats the loosely attached seals. Additionally, dropping the cartridge, subsequent to arrival can also lead to significant toner leakage. The leaking cartridge thus, may be covered in wasted toner before it is installed, soiling the printer interior and the installer.
FIG. 1 illustrates a seal utilized, in particular, in IBM Series 4019/14028/4029/40391/4049 printer cartridges. The toner tank 20 and developer roller structure 22 are shown separated from the remaining cartridge shell and photosensitive drum, which are normally attached, but have been omitted for clarity. The tank 20 includes a rotating agitator 24 to which the seal strip 26 is joined at one end 28. The seal strip 26 lays along the feed slot 30 of the tank 20 that leads into the developer roller structure 22. A series of metering rollers (not shown) are provided within the developer roller structure 22 for dispensing a predetermined quantity of toner from the tank 20 into the developer roller structure 22. These metering rollers will be described further below.
The prior art seal 26 is attached over the slot 30 with a low-tack contact adhesive. When the agitator 24 rotates, in response to the gear wheel 32 (shown in phantom), during operation of the printer, it rolls the seal 26 onto the axle 33 of the agitator 24, separating it from the slot 30. The rolled-up seal remains twisted around the agitator 24 throughout the subsequent operation of the cartridge. An advantage of the self-removing seal 26 is that it is automatically removed upon start-up of the printer without intervention by the operator. However, a major disadvantage is that the seal is, by necessity, only lightly adhered to the slot 30. It is, thus, prone to leakage and rupture during shipment. In addition, the far end 34 of the slot 30, adjacent the attached end 28 of the seal 26 is often poorly seated against the slot 30 and provides a ready opening through which toner can leak.
Thus, the prior art seal system of FIG. 1 exhibits several weaknesses that limit its effectiveness. The seal 26, which is generally constructed from a piece of relatively thick fabric ribbon takes up room inside the tank, reducing the amount of toner that can be placed within the tank 20. The seal 26, due to its weak adhesion to the slot 30, cannot withstand a strong pulse of hydraulic pressure which could result from a completely filled toner tank. Thus, toner levels are usually maintained at only approximately 3/4 of the tank capacity to reduce; "pressures" within the tank during rough handling.
Attempts have been made to overcome the disadvantages of the self-removing seal shown in FIG. 1 by providing an operator-removed seal (not shown) having a pull tab that exits the tank. The operator pulls the tab, which removes a more-securely adhered seal from the tank feed slot. However, this seal is still prone to leakage and the exit hole through which the pull tab is located provides yet another passage for toner leakage. In addition, the cartridge can be installed and operated without removing this type of seal and substantial time, and paper, can be wasted before the operator realizes that the seal has not yet been removed, since the cartridge can run with the seal still in place.
It is, therefore, an object of this invention to provide a toner cartridge seal that provides a more-reliable and positive seal during shipment. This seal should enable the toner tank to be filled further and should resist outward pressures of toner during rough handling. The seal should be located so that its presence is obvious to an operator, and should be easily removable prior to installation of the cartridge within a print engine. Finally, the seal should be easy to install during manufacture of the cartridge and inexpensive and easy to manufacture.